@popcornmix reminded me just now that Linux 4.3 has dropped non-Device Tree support.
Latest 4.3 kernel has dropped non-DT support. That means “platform” devices (stuff registered from bcm2708.c) no longer exist and must be registered from DT. So correct way to get snd-bcm2835 module is not with modprobe, but with dtparam=audio=on in config.txt.
If you add dtparam=audio=on in to config.txt, it should work, and you won’t need to modprobe snd_bcm2835 anymore. We’ll get this added to My OSMC → Pi Config for next update.
CC @Karnage
Cheers